<!DOCTYPE html>
<svg>
  <defs>
    <g id="outer">
      <symbol id="sym">
        <rect width="50" height="100" fill="green"/>
      </symbol>
      <use xlink:href="#sym"/>
      <use xlink:href="#sym" x="50"/>
    </g>
  </defs>
  <use xlink:href="#outer"/>
</svg>
